Technical session talks from ICRA 2012

TechTalks from event: Technical session talks from ICRA 2012

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Micro - Nanoscale Automation

Nanowire field-effect transistors (nano-FETs) are nano devices capable of highly sensitive, label-free sensing of molecules. However, significant variations in sensitivity across devices can result from poor control over device parameters, such as nanowire diameter and the number of electrode-bridging nanowires. This paper presents a fabrication approach that uses wafer-scale nanowire contact printing for throughput and uses automated nanomanipulation for precision control of nanowire number and diameter. The process requires only one photolithography mask. Using nanowire contact printing and post processing (i.e., nanomanipulation inside scanning electron microscope), we are able to produce devices all with a single nanowire and similar diameters at a speed of ~1 min/device with a success rate of 95% (n=500). This technology represents a seamless integration of wafer-scale microfabrication and automated nanorobotic manipulation for producing nano-FET sensors with consistent response across devices.

Peeling delicate retinal membranes, which are often less than five microns thick, is one of the most challenging retinal surgeries. Preventing rips and tears caused by tremor and excessive force can decrease injury and reduce the need for follow up surgeries. We propose the use of a fully handheld microsurgical robot and vision-based virtual fixtures to enforce helpful constraints on the motion of the tool. Our key contribution is using only visual information to reduce and limit forces during vitreoretinal surgery: no force feedback is used in the control system. Utilizing stereo vision and tracking algorithms, the robot activates motion-scaled behavior as the tip nears the surface, providing finer control during the critical step of engaging the membrane edge. A hard virtual fixture just below the surface bounds the total downward force that can be applied. Furthermore, velocity limiting during the peeling helps the surgeon maintain a smooth, constant force while lifting and delaminating the membrane. On a retinal phantom consisting of plastic wrap stretched on top a rubber slide, we demonstrate a reduction of maximum force by 40-70%.

This paper presents a manipulation system capable of five degree of freedom (5-DOF) control of a magnetic nanoagent (3-DOF position, 2-DOF orientation) implemented on an inverted microscope. Magnetic fields up to 50 mT and gradients up to 5 T/m at frequencies up to 6 kHz can be achieved. The independent generation of field and gradient vectors enables holonomic 5-DOF wireless magnetic manipulation at the nanoscale. Multiple types of motion were investigated for nickel nanowires of different lengths and analyzed using resistive force theory.

The success of assembly and manipulation tasks is highly dependent on the precision of robotic positioners employed. In turn, precision metrics for robots depend on the kinematic design, choice of actuators, sensors, and control system. In this paper, we investigate the effect of parametric uncertainties on the robot precision using interval analysis. The advantage of interval analysis is that it provides rigorous bounds on the effects of errors in terms of interval numbers. Two types of errors are considered: geometric errors due to link and joint parameter uncertainties, and sensing errors due to inaccurate measurement of joint positions. We show that modeling and simulation of these uncertainties using intervals can provide useful insight into the evaluation of manipulator precision for a given task. In particular, simulation results are offered to predict the required tolerances in a peg-in-hole microassembly operation. It is illustrated that the presented approach can replace computationally more expensive Monte-Carlo simulations to estimate the effect of uncertainties.